1. Field of the Invention
The present invention relates to improving the performance of countermass-based mechanisms for recoil control in projectile launchers.
2. General Background of the Invention
In any projectile-firing device, Newton's third law requires that the recoil caused by the firing of the projectile exactly balances the momentum carried by the projectile and the exhaust gasses. Recoil resulting from the momentum of the exhaust gases is called “secondary recoil”. Secondary recoil can be reduced to acceptable levels via the use of ports. Ports are holes in the forward end of the barrel of a projectile launcher that release the exhaust gasses radially just before the projectile exits the barrel. Since the gasses are released radially there is little net transfer of momentum to the body of the projectile launcher. Recoil resulting from the momentum of the projectile is called “primary recoil”. There is no way to alter the total amount or direction of primary recoil without affecting the velocity or direction of the projectile, usually an undesirable outcome.
Uncompensated recoil causes both excessive wear and tear on the supporting mechanism (possibly a person) as well as a tendency to knock the projectile launcher out of alignment with the target. These undesirable effects are due more to the way in which the recoil is distributed over time than to the total amount or direction of the recoil. Thus, changing the way in which the recoil is distributed over time can be used to mitigate the undesirable effects without changing the total amount or direction of the recoil. This is usually accomplished by slowing the transfer of the recoil to the body of the projectile launcher or its supporting mechanism. This spreads the recoil experienced by the projectile launcher or its supporting mechanism across more time, reducing “peak recoil”, which is the greatest amount of recoil experienced by the projectile launcher or its supporting mechanism at some moment in time during the process of launching a projectile. While peak recoil is usually blamed for the worst of the effects caused by recoil, it is possible that altering other aspects of the distribution of recoil over time may be of benefit in mitigating the undesirable effects of recoil. The present invention makes possible the adjustment of various aspects of the distribution of recoil over time including both peak recoil and aspects of recoil other than peak recoil.
There are two approaches to controlling primary recoil that have been in common use at various times:                1. Increase the mass of the projectile launcher. When the same amount of recoil must move a larger mass it can only accelerate it to a proportionally smaller velocity. Unfortunately this approach has the disadvantage of making the projectile launcher substantially heavier. This approach has two variants:                    a) Use a stationary weight. Using this method the effects of the recoil are lessened solely by the increased mass of the projectile launcher combined with the weight.            b) Use a moving weight. Using this method the body of the projectile launcher moves faster than the weight, which catches up later. As it does, the momentum contained in the moving weight is transferred to the body of the projectile launcher. The time during which the weight is moving adds to the time that it takes the entirety of the recoil to be transferred to the body of the projectile launcher.                        2. Upon firing, cause a countermass to move in such a fashion as to cancel out the primary recoil. This approach has the following two variants:                    a) Allow the countermass to continue traveling rearward until after it has left the projectile launcher. This approach has the disadvantage of creating an area of intense danger directly behind the projectile launcher, through which the ejected countermass travels.            b) Do not allow the countermass to leave the projectile launcher. This approach has the following three variants:                            i. Use of deformable means. This method slows the transfer of momentum from the countermass to the body of the projectile launcher by requiring it to pass through a deformable mass at some point in the process. The time that it takes the mass to deform is added to the time that it takes for the momentum to be completely transferred to the body of the projectile launcher. Depending on the type of material used, the mass may or may not return to its original shape after use.                ii. Use of friction. This method slows the transfer of momentum from the countermass to the body of the projectile launcher by requiring it to be transferred via friction between the moving countermass and the body of the projectile launcher.                iii. Use of impact. This method delays the transfer of momentum from the countermass to the body of the projectile launcher until the countermass hits a stop.                                                
The mechanism disclosed herein is of type 2b. Many mechanisms of this type have been tried. A representative sampling is discussed below, in chronological order.
In British patent number GB126336 the patentee discloses a mechanism whereby peak recoil can be reduced in a firearm. The mechanism is composed of two parts. First, a section of barrel, closed at the rearward end, extending behind the projectile and narrowing somewhat in diameter as it progresses rearward. Second, a cylindrical cup composed of brass (or another soft metal), with a diameter essentially the same as that of the rearward barrel, placed directly behind the propellant charge, with the opening oriented directly towards the projectile and the opening at the front of the barrel. Upon firing, the countermass (the cup) is propelled rearwards along the barrel. Friction between the cup and the inside surface of the barrel slows the cup as it travels rearward. The decreasing diameter of the barrel eventually forces the cup to a stop, at which point all of the rearward momentum has been transferred to the body of the gun. See also related British patents numbered GB125652 and GB125605, each with one additional author. In GB125652 the cup leaves the rearward barrel rather than being forced to a complete stop within the rearward barrel, and in GB125605 an inertial mass leaves the rear of the gun, and the transfer of momentum from the inertial mass to the gun is assisted by means of a very tight spiral of rifling in the portion of barrel along which the inertial mass travels.
There are several practical problems with this approach which render it unusable as a recoil reduction device. First, according to the disclosure the barrel and cup are necessarily of different metals, the cup being the softer, to avoid wear on the barrel. One side effect of this is that with each use metal would rub off of the cup and plate the inner surface of the barrel. Because of this each use would change the amount of friction between the barrel and successive cups, significantly altering the performance of the gun. Second, differences in the amount of expansion that different metals undergo at different temperatures would change the fit between the cup and the barrel. A gun manufactured in a temperate environment might not function properly in a desert or arctic setting. Even the heat generated by friction as the cup travels along the barrel might be enough to cause misfires or worse. This is particularly troublesome given that the successful operation of the mechanism is strongly dependent on having an exact fit between the cup and the barrel. Third, the mechanism is so dependent on having an exact fit between cup and barrel that the presence of small amounts of dust or dirt in the barrel could jam the cup long before it reached the end of the barrel, with unpredictable results.
In U.S. Pat. No. 3,018,694 the patentee discloses a mechanism whereby peak recoil can be reduced in a firearm. The mechanism is composed of a main, reciprocating barrel down which the bullet travels, connected to a piston housed inside of an auxiliary barrel located beneath the main barrel. Upon firing, the main barrel moves backwards towards the shooter, carrying the piston in the auxiliary barrel with it. Past a certain point, compressed air from behind the bullet is fed from the main barrel into the auxiliary barrel at a point between the piston and the shooter. The compressed air acts as a brake on the piston, and through it the main barrel, transferring momentum from the main barrel into the body of the firearm. Upon complete breaking of the piston the compressed air behind the piston, and a return spring, cause the piston and main barrel to return to their initial position. The primary advantage claimed by the patentee is that the mechanism does not have to be adjusted to compensate for different loads. Heavier loads will produce more gas pressure, providing the greater breaking necessary for the faster-moving piston without the need for adjustment by the shooter.
As with all of the piston-based approaches most of the problems are those related to the use of an unnecessarily complex mechanism. One problem is the unnecessarily high cost of construction, including the cost of the various machined components and their assembly into the final device. Other problems include the costs and efforts associated with cleaning, maintaining, durability, repair, and the necessity for the stockpiling of replacement parts. The fact that successful functioning requires that several parts move smoothly against each other in a controlled fashion makes the mechanism vulnerable to dirt, dust and sand. The fact that the same force that propels the bullet forwards also propels the reciprocating barrel backwards, and that some of the propellant gasses are bled from inside of the barrel before the bullet exits the barrel, robs the bullet of power. Finally, the mechanism is unnecessarily heavy, adding to the weight of the gun.
In U.S. Pat. No. 4,088,057 the patentee discloses a mechanism whereby peak recoil can be reduced in a firearm. The mechanism is composed of a closed auxiliary barrel, containing a weighted piston, mounted atop the main barrel. When the gun is fired some compressed air is bled from the main barrel into the auxiliary barrel, driving the piston rearwards. The rearward momentum is held by the piston until it approaches the rearward most portion of the auxiliary barrel. At this point air trapped between the piston and the rearward closed end of the auxiliary barrel causes the piston to slow, transferring momentum to the gun via the compressed air. Upon completion of this movement, the piston is returned to its original position by a spring.
The problems with this mechanism are basically the same as those of the piston-based device disclosed in U.S. Pat. No. 3,018,694, but somewhat reduced due to improvements in the overall design. Most noteworthy is that in this mechanism the main barrel does not reciprocate, removing one of two mechanisms responsible for decreasing the power of the bullet.
In U.S. Pat. No. 6,578,464 the patentee discloses a mechanism for reducing peak recoil. The mechanism is described in the context of an explosives disruptor, which device is used to set off an explosive device from a distance by firing a projectile into it. The mechanism consists of a two part barrel. The first part is an inner, sliding barrel, with a closed breech end, similar to that used in some conventional firearms today. The second part is an outer, non-moving barrel, enclosing the inner barrel and connected to the gun body. The inner barrel slides along the outer barrel upon firing. The outer surface of the inner barrel contains a widened area that is directly in contact with the inner surface of the outer barrel. As the inner barrel recoils, momentum is transferred to the gun body via the friction between the inner and outer barrels.
The problems with this approach are similar to those of the friction-based approach disclosed in British patent number GB126336 discussed above. Continued friction between the widened area of the inner barrel and the inner surface of the outer barrel creates heat, wearing of the parts that are in constant contact with each other, plating of the inner surface of the outer barrel with material from the widened part of the inner barrel, etc. The friction generated heat creates the same risk of differential expansion of different parts of the mechanism, and the potential negative consequences thereof, which were present in the device disclosed in British patent number GB126336. Finally, the use of a reciprocating barrel robs the projectile of power just as was the case with the device disclosed in U.S. Pat. No. 3,018,694.
In U.S. Pat. No. 7,302,773 the patentee discloses a device for delaying peak recoil that consists of a two part barrel, the rearmost section containing the cartridge and constructed so as to slide backward upon firing, continuing until it hits a stop. In this fashion the recoil is delayed from affecting the gun body until after the bullet has left the barrel, supposedly improving the accuracy of the weapon. This approach is problematic in two regards. First, it doesn't decrease peak recoil; it only delays peak recoil until the moving portion of the barrel hits the stop. Second, some of the power used to propel the bullet is diverted into moving the moving portion of the barrel, robbing the bullet of power.
In U.S. Pat. No. 7,398,614 the patentees (who are also the named inventors of U.S. Pat. No. 7,302,773, discussed above) disclose a mechanism for delaying peak recoil that consists of a barrel, anchored to the gun body, down which the bullet travels, a forward sliding mass surrounding the barrel, and a rearward sliding mass that butts up against the rear of the barrel and contains the cartridge. Upon firing the force of the expanding gasses within the barrel pushes the forward sliding mass forwards, and the rearward sliding mass rearwards, in such a fashion that the recoil that would normally be transmitted into the gun body is instead transferred into the two sliding masses. Eventually the sliding masses hit prepositioned stops anchored to the gun body, at which time they cease sliding and their momentum is transferred through the stops into the gun body. The problems with this mechanism are the same as those discussed with the simpler mechanism disclosed in U.S. Pat. No. 7,302,773.
In international patent number WO2010051898 the applicants disclose a mechanism for reducing peak recoil in a weapon that uses a backward sliding barrel with a closed breech end. The recoil reduction mechanism consists of a deformable mass situated between the breech of the barrel and the weapon mounting. Upon firing, the recoil is transferred first to the barrel, then through the backward sliding barrel into the deformable mass, causing it to deform, thus causing the recoil to be transferred to the weapon's mounting over a longer period of time, reducing peak recoil. The primary problem with the mechanism described in this patent is that it requires manual replacement of the deformed mass after use, as well as manual resetting of the positions of the various components of the weapon, including the barrel.